1. Field of the Invention
The present invention relates to package structures and fabrication methods thereof, and more particularly, to a package structure having a Micro Electro Mechanical System (MEMS) element and a fabrication method thereof.
2. Description of Related Art
Micro Electro Mechanical System (MEMS) techniques integrate electrical and mechanical functions into a single element using micro-fabrication technology. An MEMS element is disposed on a chip and covered by a shield or packaged with an underfill adhesive so as to protect the MEMS element from the external environment.
FIG. 1 is a cross-sectional view of a conventional package structure having an MEMS element. Referring to FIG. 1, the package structure comprises a quad flat no lead (QFN) type lead frame 10; a chip 11 disposed on the lead frame 10; an MEMS element 12 disposed on the chip 11; a lid 13 disposed on the chip 11 to cover the chip 11; an aluminum layer 14 disposed on the top surface of the lid 13; a plurality of bonding wires 15 electrically connecting the chip 11 and the aluminum layer 14 to the lead frame 10, respectively; and an encapsulant 16 encapsulating the lead frame 10, the chip 11, the lid 13, the aluminum layer 14 and the bonding wires 15.
However, due to the use of the lead frame 10 and the lid 13, the package structure becomes too thick.
Further, using the bonding wires made of gold for electrically connecting the MEMS element and the lead frame easily results in slow signal transmission and low sensitivity. Also, gold wires incur high fabrication costs. Furthermore, the encapsulant encapsulating the MEMS element and the gold wires leads to increase of the thickness of the overall package structure. Therefore, such a package structure does not meet the trend of miniaturization and low cost.
Therefore, it is imperative to provide a package structure having an MEMS element that has reduced size, low cost and improved signal transmission efficiency.